Sanitary napkins



March 14, 1967 R. BLAKE SANITARY NAPKINS Filed March 9, 1961 United States Patent *Ofifice 3,303,826 SANITARY NAPKINS Lawrence R. Blake, Cumberland, Md., assignor to Celanese Corporation, a corporation of Delaware Filed Mar. 9, 1961, Ser. No. 94,598 16 Claims. (Cl. 128-290) This invention relates to improvements in sanitary napkins, particularly sanitary napkins of the type having an absorbent pad body and a cover fabric.

Several properties are critically important in the cover fabrics of sanitary napkins. This fabric must be sufficiently soft so as not to be irritating, inert to the aqueous fluids associated with menstruation, non-allergenic and probably most important, the fabric must permit the unimpeded passage therethrough of the aqueous menstrual fluids into the absorbent pa-d body.

It'is an object of this invention to provide a sanitary napkin cover fabric having the aforementioned desirable properties, particularly a fabric which permits the unimpeded passage of aqueous fluids.

It is another object of this invention to provide a process for treating the yarns of the cover fabrics in order to control the ability of these cover fabrics to permit the passage of aqueous fluids.

It is another object of this invention to provide novel compositions which act both as yarn lubricants and yarn conditioners for controlling the ability of cover fabrics containing conditioned yarns to permit the passage of aqueous menstrual fluids.

Other objects and advantages will become apparent in accordance with the following description in which all proportions are by weight unless otherwise stated.

In accordance with one aspect of this invention, there is provided a sanitary nap-kin having a cover fabric comprising interlaced yarns carrying a yarn lubricant and conditioning agent which has been so modified as to impart to the fabric a capillarity factor in the range of from about 6 to 9 and most preferably from 7 to 8. In the commercial high speed weaving or knitting of fabrics, the yarns are moved rapidly over guides and other mechanized elements and are subjected to conditions conducive to the production of static electricity. To cope with these conditions, it is the usual practice to use yarns carrying lubricating agents to give the yarns desirable frictional qualities and conditioning agents to impart antistatic properties to said yarns. A suitable type of composition for this purpose is described in US. Patent 2,575,399. It has now been found that fabrics made from the usual lubricated and conditioned yarns do not have the optimum properties for use as cover fabrics in sanitary napkins in that the capillarity of cover fabrics incorporating such yarns is too high. Where such cover fabrics of high capillarity are used in sanitary napkins, the menstrual fluids preferentially flow along the cover fabric rather than through the cover fabric into the inner absorbent body of the napkin. Thus, the cover becomes saturated before much fluid has passed into the absorbent body.

On the other hand where yarns having a capillarity which is too low are used in cover fabrics, such cover fabrics will permit the passage of very little menstrual fluid into the inner absorbent body of the pad. Instead the fluid will form liquid beads on the cover fabric. Such a condition is very uncomfortable to the user of the sanitary napkin.

In order to determine the capillarity factor of a given fabric, a strip of the fabric, from 3.2 to 3.2 centimeters in width, is suspended with its lower end immersed in water. The capillarity factor is determined by the distance above the water surface that water rises by the capillary action of the fabric. In order to facilitate the 3,398,826 Patented Mar. 14, 1967 determination of the water rise in the fabric, the water may conveniently contain an indicator in such quantities as would not affect the capillary action of the fabric.

The capillarity factor is equal to the number of centimeters that the Water in the strip will rise above the water surface in 42 hours.

The capillarity factor was determined as follows. A 38-centimeter strip, 3.5 cm. wide, of the cover fabric to be tested was suspended normal to a flat surface with the lower end of the strip touching the surface. 200 ml. of Water containing 0.1% of an indicator fluorescent under ultraviolet light was placed in a wide mouth 250-ml. Erlenmeyer flask. The flask was then placed under the suspended strip so that the strip was suspended into the flask. After 42 hours, there was measured the rise of the liquid above the surface of the liquid in the flask which surface was 5.5 cm. above the flat surface. Determination of the extent of rise may be aided by using an ultraviolet light in which the liquid-containing areas of the strip will be fluorescent. The distance in centimeters of the liquid rise in the strip is the capillarity factor. During the 42-hour period, the liquid level in the flask may change e.g., change due to evaporation. The surface of the liquid was maintained at 5.5 cm. above the fiat surface by adding distilled water. This determination was conducted at 21 C.

It has now been found that a fabric of suitable capillarity may be obtained by including a sufficient proportion of additional water-repelling agent on the yarn in conjunction with the usual lubricating and anti-static components. Thus, the capillarity of the yarn carrying a composition of the type described in U.S. Patent 2,575,399 or US. Patent 2,676,924 may be modified by including in that composition an acetate of a polyvalent metal such as aluminum or zirconium. Such acetate salt is preferably added in aqueous solution to the above composition. These acetate salts, particularly aluminum acetate act to increase the water repellency of the composition and thereby lower the capillarity factor of the fabric to the above-described preferable ranges.

One preferred modified conditioning and lubricating agent which has been found to provide thermoplastic yarns particularly cellulose acetate with suitable capillarity factors comprises a mixture of mineral oil, a partial ester of phosphoric acid and a long chain aliphatic alcohol and an alkylolamino ester of a long chain aliphatic acid modified by the addition of aluminum acetate. However, it has been found even more advantageous if the conditioning and lubricating agent described is modified by a composition for increasing water repellency which comprises said acetate salt and a water-repellent wax in aqueous emulsion. Where the acetate salt and water-repellent wax composition are so incorporated into the conditioning and lubricating agent, it is preferable that the agent be applied to the cover fabric in aqueous emulsion which further includes an emulsifying agent, an alkyl phenol and a lower alkanol. v

The above-mentioned modified lubricating and conditioning composition is advantageously applied as an aqueous emulsion preferably containing 0.2 to 1.0% of the acetate salt, preferably aluminum acetate. The acetate salt is admixed into the emulsion as an aqueous solution of the acetate salt e.g., 2 to 10% of 10% aqueous solution of the acetate salt. In combination with said acetate salt, there are preferably 5% to 10% of the above-mentioned water-repellent wax which is preferably a wax fonning an anionic soap type of emulsion in water e.g., metal stearates such as aluminum or chromium stearate; 1 to 2% of a lower alkanol such as isopropyl alcohol, methyl alcohol, butyl alcohol or ethyl alcohol, which alcohols act primarily as emulsion stabilizers. The combination is emulsified in 70 to 85% of Water which further contains 5% to of an emulsified composition comprising:

(A) 40 to 55 parts mineral oil which is a refined paraffinic petroleum product having a viscosity at 100 F. in the range of 50 to 100 Saybolt Universal seconds. (B) to 25 parts of a partial ester of phosphoricacid 'With a long chain aliphatic alcohol which is formed by reacting the desired alcohol such as decyl alcohol, tridecyl alcohol, lauryl alcohol, n-octyl alcohol, n-decanol, n-nonyl alcohol or n-undecyl alcohol or combinations of said alcohols with a slight stoichiometric excess of phosphorous pentoxide to form a primary phosphoric acid ester.

(C) to parts of an alkylolamino ester of a long chain aliphatic acid which is obtained by the reaction of an alkylolamine suchas triethanolamine, diethanolamine, 'triisopropanolarnine or 2 amino-Z-methyl l propanol with a mixture of straight chain aliphatic acids comprising essentially lauric acid and having an average of about 11 to l2 carbon atoms in the alkyl chain, exclusive of the carboxyl group present. The carbon chain length usually varies from about 10 to 18 carbon atoms. This aliphatic acid mixture may be obtained as a product of the saponification of commercial coconut oil. The saponification reaction yields glycerin and the desired mixture of long chain aliphatic acids which may be separated from the glycerin in a suitable manner and then esterified to yield the desired alkylolamine ester. In forming the aliphatic acid alkylolamine ester, the hydroxy radical of the carboxyl group of the long chain aliphatic acids reacts with one of the hydroxy groups of the triethanolamine, for example, splitting otf water and forming the diethanolaminoethyl ester of the long chain aliphatic acid. The reaction may be effected employing the necessary stoichiometric proportions of the long chain aliphatic acid mixture and triethanolamine at a temperature of about 110 C. and continuing the reaction until the viscosity of the reaction product at 100 F. is reduced to about 320 to 340. The reaction may be effected at temperatures up to about 200 C. employing any alkylolamine and fatty acid or mixture of fatty acids which. is not volatile at the temperature employed. The viscosity is determined in the Saybolt Universal viscometer at 100 F. and, Where the term viscosity is embodied hereinafter, it is to be understood as being that obtained in the Saybolt Universal viscometer at a temperature of 100 F. I

(D) 2 to 4 parts of an alkyl phenol which is preferably ditertiary-arnyl phenol. Other suitable alkyl phenols include ditertiary-butyl phenol, mixtures of ditertiary-amyl and ditertiary-butyl phenol, preferably containing equal portions of each, diamyl phenol, triamyl phenol and di butyl-m-cresol and ditertiary-butyl-p-cresol.

(E).15 to 20 parts of a non-ionic emulsifying agent preferably a polyoxyethylene sorbitan ester such as polyoxyethylene sorbitan mono oleate Other operable emulsifying' agents include polyoxyethylene, ,sorbitan, monolaurate, pal-mitate and stearate.

(F) l to 3 parts of water.

This novel lubricating and conditioning 'emulsion'is preferably prepared by heating the water to l00-180 F. and then adding in the following order, the lubricant and conditioning composition, the wax emulsion, the complex salt and the lower alkanol while continuously stirring the mixture. Stirring is continued until a smooth homogeneous blend is obtained.

The aforementioned composition may be used to lubricate and condition other cellulose materials including cellulose esters such as cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate propionate-butyrate and cellulose ethers, such as ethyl cellulose and benzyl cellulose as the composition may also be used on the other thermoplastic yarns which will be hereinafter set forth.

The lubricant and conditioning composition carried which are not included. The fabrics are preferably knit 'and most preferably tricot knit. The yarns are preferably thermoplastic continuous filament yarns but staple fiber yarns may also be used. The chemical composition of the yarns may vary widely'and, for example, may constitute nylon, polyesters such as polyethylene terephthalate, polymers and/or copolymers of olefins or vinyl compounds such as ethylene, propylene, vinyl chloride, vinylidene chloride, acrylonitrile and regenerated cellulose fibers. Preferably, the yarns comprise organic acid esters of cellulose such as the lower alkanoic acid esters, e.g., cellulose acetate. Cellulose acetate yarns treated with the modified lubricating and conditioning compositions of this invention provide excellent sanitary napkincovei's' which are soft, inert to menstrual fluids, non-allergenic, non-irritating and have desirable capillarity factors The capillarit'y factor will vary with the nature of the fabric, that is denier of the yarns and the weight of fabric per square yard as well as with the nature of the lubricant used on the yarns. In sanitary napkins, the yarns of the cover fabric are preferably less than 100 denier and the cover fabric preferably has a weight of from 0.40 to 0:80 ounce per square yard. In accordance with another aspect of my invention, 1 have found that if the yarns are treated with compositions which decrease the hydrophilicity of the yarns, the capillarity factor of the fabric may be decreased arid if the yarns are treated with compositions which increase the hydrophilicity of the yarns, the capillarity factor of the fabric may be increased. For example, I have found that aluminum acetate applied as a 20% aqueous solu-' tion to regenerated cellulose yarn substantially decreases the capillarity factor of such yarn.

' On the other hand, the conditioning fluids set forth in U.S. Patent 2,385,423 have been found to increase the hydrophilicity of the yarns. (For example, a composition consisting of 55.05 white mineral oil having a viscosity of 50 on the Saybolt Universal viscometer at 100 F., 22.2% oxidized peanut oil, 10.35% oleic acid, 6.1% butyl acetyl ricinoleate, 3. 5% ditertia'ry amyl phenol and 4.8% triethanolamine has been found to be very eifective in this respect.) According to this aspect of the inven tion, the hydrophilicity-affecting compositions may be applied to the fiber filaments before they are made into yarns or even directly to the fabric containing the yarns, but it is preferable to apply the composition to the yarns prior to the weaving or knitting operation. In the latter case, the hydrophilicity-affecting composition may be in corporated into and form part of the yarn lubricating and conditioning composition to produce the previously described lubricating and conditioning compositions.

The accompanying drawing which is a cross-section of a sanitary napkin immediately prior to wrapping of the cover layer thereabout will illustrate the sanitary napkin of this invention. The layers comprise three sheets of tissue paper 10, a web of viscose fiber 11, two

sheets of tissue paper 12, a layer of wood pulp fiber 13, a sheet of water repellent tissue 14, four sheets of tissue 15, another layer of wood pulp 16, another sheet of tissue 17, eight sheets of tissue 13 and cover layer 19, the yarns of which carry the modified lubricating and conditioning composition of this invention.

The following example will illustrate the preparation of the novel composition of this invention.

Example To 69 parts of water maintained at a temperature of to F., there is added with continuous stirring parts of an aqueous emulsion of chromium stearate (50% solids), 10 parts of a 10% aqueous solution of aluminum acetate, 1 part of isopropyl alcohol and 10 parts of a composition comprising 41.9% of an acid -refined mineral oil having a viscosity of 50 seconds at 100 F., 17.5% of mixeed phosphate formed by reacting tridecyl alcohol, decyl alcohol and phosphorus pentoxide in the molar ratio of 3:3:1, 2.9% of ditertiary-amyl phenol, 19.9% of diethanolamino-ethyl ester of lauric acid, 16.1% of polyoxyethylene sorbitan mono oleate and 1.6% of water. The mixture is stirred until a smooth and homogeneous mixture is obtained.

The mixture is then applied by rollers to secondary cellulose acetate continuous filament yarns having an acetyl value of from 54.5 to 55.1 calculated as combined acetic acid. The yarns are of 55 denier and have 22 filaments per yarn, and the mixture carried by the yarns comprises 2.5% of the yarn weight. The yarns are warp knit to form a fabric having a weight of 0.53 ounce per yard. The fabric produced is soft, inert to menstrual fluids, non-allergenic and non-irritating.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention what I desire to secure by Letters Patent is:

1. In a sanitary napkin, an interlaced cover fabric comprising yarns of less than 100 denier, said fabric having a weight of from 0.4 to 0.8 ounce per square yard and a capillarity factor from 6 to 9.

2. A sanitary napkin according to claim 1, wherein said yarns are continuous filament yarns.

3. A sanitary napkin according to claim 1, wherein said yarns are cellulose acetate.

4. A sanitary napkin according to claim 1, said cover fabric being knit.

5. A sanitary napkin according to claim 4, said cover fabric being tricot knit.

6. A sanitary napkin having as a cover a tricot fabric of continuous filament yarns of less than about 100 denier, said fabric weighing from about 0.4 to 0.8 ounce per square yard, and carrying a conditioning and lubricating composition comprising a mineral oil, a partial ester of phosphoric acid and a long chain aliphatic alcohol, an alkylolamino ester of a long chain aliphatic acid and aluminum acetate, said conditioned and lubricated fabric having a capillarity factor of from about 6 to 9.

7. The sanitary napkin of claim 6 wherein said conditioning and lubricating composition contains 0.2 to 1.0 part by weight of aluminum acetate.

8. A tricot fabric of continuous filament yarns of less than about 100 denier, said fabric weighing from about 0.4 to 0.8 ounces per square yard, and carrying a conditioning and lubricating composition comprising a mineral oil, a partial ester of phosphoric acid and a long chain aliphatic alcohol, and alkylolamino ester of a long chain aliphatic acid and aluminum acetate, said conditioned and lubricated fabric having a capillarity factor of from about 6 to 9.

9. A tricot fabric according to claim 8 knit of cellulose acetate yarns.

10. The tricot fabric of claim 8 wherein said conditioning and lubricating composition contains 0.2 to 1.0 part by weight of aluminum acetate.

11. The tricot fabric of claim 9 wherein said conditioning and lubricating composition contains 0.2 to 1.0 part by weight of aluminum acetate.

12. A tricot fabric useful as a cover fabric for a sanitary napkin, said fabric comprising interlaced filament yarns of less than about 100 denier, weighing from about 0.4 to 0.8 ounce per square yard, and carrying a conditioning and lubricating composition comprising:

(a) water;

(b) 0.2 to 1.0 part of an acetate of a polyvalent metal;

and

(c) 5 to 10 parts of a mixture comprising (1) 40 to 55 parts of mineral oil; v

(2) 15 to 25 parts of a partial ester of phosphoric acid and a long-chain aliphatic alcohol; and

(3) 20 to 25 parts of an alkylamino ester of a long-chain aliphatic acid,

said conditioned and lubricated fabric having a capillarity factor of from about 6 to 9.

13. The tricot fabric of claim 12 wherein said composition further includes 5 to 10 parts of a water-repellent wax.

14. The tricot fabric of claim 13 wherein said composition further includes 1 to 2 parts of a lower alkanol and wherein mixture (0) of said composition includes 2 to 4 parts of an alkyl phenol.

15. A tricot fabric useful as a cover fabric for a sanitary napkin, said fabric comprising interlaced cellulose acetate filament yarns of less than about denier, weighing from 0.4 to 0.8 ounce per square yard, and carrying a conditioning and lubricating composition comprising:

(a) water;

(b) 0.2 to 1.0 part of aluminum acetate;

(c) 5 to 10 parts of a metal stearate selected from the group consisting of aluminum stearate and chromium stearate;

(d) 1 to 2' parts of a lower alkanol; and

(e) 5 to 10 parts of a composition comprising (1) 40 to 55 parts of mineral oil;

(2) 15 to 25 parts of a partial ester of phosphoric acid and a long-chain aliphatic alcohol of the type formed by reacting a slight stoichiometric excess of phosphorus pentoxide with at least one alcohol selected from the group consisting of decyl alcohol, tridecyl alcohol, lauryl alcohol, n-octyl alcohol, n-decanol, n-nonyl alcohol, and n-undecyl alcohol;

(3) 20 to 25 parts of an alkylamino ester of a long-chain aliphatic acid of the type resulting from the reaction of an alkyl amine selected from the group consisting of triethanolamine, diethanolamine, triisopropanolamine, or 2- amino-2-methyl-l-propanol with a mixture of straight chain aliphatic acids having an average of about 11 to 12 carbon atoms in the alkyl chain, exclusive of the carboxyl group present;

(4) 2 to 4 parts of ditertiary-amyl phenol; and

(5) 15 to 20 parts of polyoxyethylene sorbitan monooleate.

16. A conditioning and lubricating composition consisting essentially of:

(a) water;

(b) 0.2 to 1.0 part of aluminum acetate;

(0) 5 to 10 parts of a metal stearate selected from the group consisting of aluminum stearate and chromium stearate;

(d) 1 to 2 parts of a lower alkanol; and

(e) 5 to 10 parts of a composition comprising (1) 40 to 55 parts of mineral oil;

(2) 15 to 25 parts of a partial ester of phosphoric acid and a long-chain aliphatic alcohol of the type formed by reacting a slight stoichiometric excess of phosphorus pentoxide with at least one alcohol selected from the group consisting of decyl alcohol, tridecyl alcohol, lauryl alcohol, n-octyl alcohol, n-decanol, n-nonyl alcohol, and n-undecyl alcohol;

(3) 20 to 25 parts of an alkylamino ester of a long-chain aliphatic acid of the type resulting from the reaction of an alkyl amine selected from the group consisting of triethanolamine, diethanolamine, triisopropanolamine, or 2- amino-Z-methyl-l-propanol with a mixture of (5) 15 to 20 parts of poiyoxyethylene sorbitan monooleate.

References Citedby the Examiner UNITED STATES PATENTS 882,301 3/1908 Doyle 128-290 2,015,865 10/1935 Muller 117-1395 2,046,305 6/ 1936 Cleaveland 117-1395 2,340,311 2/1944 Donovan 128-285 2,407,632 9/1946 Dreyfus 28-80 2,440,141 4/1948 Donovan 128-285 2,468,876 5/1949 Hermanson 128-290 2,575,399 11/1951 Seymour 252-88 2/1954 Mailander 106-271 2/ 1954 Mailander 106-271 4/1954 Fortress et a1 252-88 1/ 1956 Fortress et a1 252-88 2/1956 Parish 128-285 7/1956 Schoenberger 28-80 8/1956 Fluck et a1 117-1395 9/1959 Harwood et a1 128-290 4/1960 Novak 117-1395 12/ 1960 Ashton et a1 128-290 FOREIGN PATENTS 1/1959 France.

12/1954 Great Britain.

RICHARD A. GAUDET, Primary Examiner.

CHARLES F. ROSENBAUM, Examiner. 

1. IN A SANITARY NAPKIN, AN INTERLACED COVER FABRIC COMPRISING YARNS OF LESS THAN 100 DENIER, SAID FABRIC HAVING A WEIGHT OF FROM 0.4 TO 0.8 OUNCE PER SQUARE YARD AND A CAPILLARITY FACTOR FROM 6 TO
 9. 